Comparative architectonic studies have resulted in a classification of the amygdaloid complex which differs somewhat from the commonly used classification (first proposed by Humphrey, 1936) by separating the cortical amygdaloid nucleus from the centromedial group and assigning it to the basolateral group, which then forms a cortico-basolateral group. The size changes of these groups and of the nucleus of the lateral olfactory tract (belonging to the centromedial group) and the large-celled part of the basal nucleus (belonging to the cortico-basolateral group) have been investigated in representatives of an ascending primate scale. In all structural complexes investigated so far, the small-celled part of the cortico-basolateral group is the most progressive. In descending order of progression there follow: the cortico-basolateral group as a whole, the amygdala as a whole, and the large-celled basal nucleus. No clear changes were found in the centromedial group as a whole, whereas the size of the nucleus of the lateral olfactory tract, which represents a small component of this latter group, shows a strong reduction. These differences in the developmental trends point to increasing or decreasing capacities of the functional (limbic and olfactory) systems, to which these structures are related.

N THE neurosurgical treatment of parkinsonian tremor, a major question to be ,answered is, where is the optimum site of target for the lesion? The present study is an attempt to evaluate the posterior ventrolateral area of the thalamus, internal capsule, medial region of the globus pallidus and posterior subthalamus. The comparative value of lesions in these structures was determined by (1) noting differences in reduction of tremor associated with insertion of electrodes, and (~) a comparison of the amount of radio-frequency electrical energy (expressed as Boyle-time factor) necessary to obtain over 75 per cent reduction in tremor. The primary objective of this presentation is to demonstrate that lesions in the posterior subthalamus are the most efficient for reducing parkinsonian tremor. Technique Patients. From a group of 150 parkinsonian patients with varying degrees of tremor and rigidity, only those patients having unilateral or bilateral tremor as the major finding were utilized for this study. Tremor was bilateral in the majority of the 58 patients although usually it was more pronounced on one side. The mean age of the patients was 58 and ranged from 41 to 80 years. All patients had been receiving a variety of medications before operation which did not satisfactorily control the tremor. Patients with bilateral tremor were replaced on medication postoperatively. Since these observations were made in patients distributed over the past 7 years, the traditionally desired 5-year detailed follow-up was not possible. The shortest period of follow-up was 4 months (3 patients). Operation. A total of 7~ operations were performed in the 58 patients. Bilateral operations were done in 6 patients and in 1 it was repeated. Repeated unilateral operations were performed in 6 and the rest of the patients had unilateral procedures. Operations were done with patients

D e p a r t m e n t of N e u r o s u r g e r y , U n i v e r s i t y of Mississippi Medicul C e n t e r . Jackson, M i s s i s s i p p i , a n d N e u r o a n a t o m i s c h e Abteilung, Max-Plnnck-I n s t i t u t f u r H i r n f o r s c h u n g , F r a n k f u r t ( M a i n ) -N i e d e r r a d , G e r m a n y ABSTRACTThe septum of the human brain was studied in relation to its location, composition and development. It was possible to divide i t into two parts: septum pellucidum, composed of fiber tracts and glia, and septum verum (true septum) which in addition to fiber tracts and glia.contain neurons arranged in a nuclear pattern. The septum verum in the human corresponds to the septum as described in lower forms. The human septum has been thought to have regressed and be nearly functionless in contrast to lower forms. However, the nucleus septalis triangularis is the only septal nucleus which regressed in development when compared to that in the brains of insectivores and primates. The rest of the septal nuclei progressively increased in size during primate development. Finally, it should be emphasized that the septum verum of the human has attained its highest degree of development in primate phylogeny. 'The materials utilized and work performed were at the Max-*Supported in part by NIH grant 04510. Planck-Institut fur Hirnforschung. Frankfurt. Germany.

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